I would assume the heat pump could be used to supplement heating of the traction battery? (AC on older models can cool the battery) If true, how does the power heating efficiency/power usage compare to using the motor stator windings to perform the traction battery heating? Are there cell/ambient temperature ranges where heating with the heat pump uses less traction battery energy than the motor(s) winding method and vice-versa. What does SMT display regarding information on heat pump energy usage, if any? BTW. hope these questions have not been asked many times before.
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Can heat pump on newer M3/MY heat traction battery?
- Thread starter rrolsbe
- Start date
The answer appears to be Yes. There is a 3-part series of videos on youtube that describe the various operating modes using the octovalve. In the second video, conditions 5-8 do battery heating. The info in the videos is from Teslas patent. So the modes actually used may be a subset of what is in the patent.
Thanks for the response, I had watched all three videos over a year ago. Maybe I missed it but do any of the heating modes use the motor(s) stator windings to create heat if needed? If it does, is it used in most cases, as a last resort due to not being as energy efficient as newer methods? Can anyone with SMT confirm power is sent to the motor windings while parked in some scenarios?
The PCS (inverter(s)) and drive unit(s) are in the coolant loop on the right side of their diagram. Used for heating in several of the different scenarios. Apparently they can also run the compressor motor 'inefficiently' to add heat directly to the refrigerant loop.
Obviously the COP would be 1 in these scenarios. But they do allow elimination of separate battery heaters, PTC heaters, and the like.
Teslabjorn has done some youtube videos with heat pump tests. He watches the power going to the stator windings with scanmytesla to see when they are used. He refers to the stator heating as "afterburners".
Yes correct, I noticed this week the following while watching SMT during my commutes:
- While -10C or warmer, AND battery is greater than 20% charge
The heat pump will draw heat from the ambient air through the Radiator+Fan and heat both the cabin and battery. Then when the battery reaches 16.5C the radiator bypass valve is activated and then active battery heating stops and the heat pump will now draw heat away from the battery. You will see at this point the battery inlet temp 1-4C colder than battery temp depending on HVAC settings. Then when the battery reaches 12C the radiator is activated again to heat both the battery and Cabin. This used up approx 1.5kW while battery heating and approx 800 watts while using the battery as a the heat source.
-While -11C and colder
I noticed in just one case this week that it used both the motor and radiator to heat up the battery. this used a whopping 3-4kw while the battery was around 0C. Again warmed up all the way to 16.5C.
- Weirdest thing i noticed in all this is that once the battery reaches 19%, the battery heating never stops. I arrived home one night at 15% battery and the battery at 17.5C. Battery heating continued even while in park. This is odd since it uses more power at a critically low level however im assuming this helps squeeze out and last bit of power.
Maybe we will get some -20C days here in Ontario soon so i can report out on what happens then more accurately.
Just an update, the latest software has changed the logic above. The car no longer is actively trying to heat up the battery up to 16.5C, instead it now just maintains the battery inlet ever so slightly above battery temp and gently warms it up. It went from 0 to 13 after my commute whereas before the update it got to 16.5 within the first 70% of my commute, both cases in similar temps like -12C.
I believe this is in response to the heat pump issues to reduce the load by prioritizing cabin heating over battery warming.
I think those videos have some, but not all, of the modes of the heat pump. There are additional modes not covered in those videos that would require some bypass valves not depicted in the videos. For example, I tried to navigate to a supercharger with the atmospheric temperature at approximately 15°C and turned the cabin HVAC to OFF. I observed that the radiator fans were on and the heat pump was extracting heat from the atmosphere and putting it into the battery, but if you watch the videos this is impossible, because the battery always comes after the chiller and the system wouldn't be capable of taking heat from the atmosphere and putting it into the battery otherwise. So I think there must be some bypass valves that are capable of making the chiller and radiator be in one loop (for atmospheric heat extraction) and the battery and liquid cooled condenser in another loop (for dumping heat into the batteries).
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